A post-processing apparatus for an image forming apparatus performs post-processing, such as stapling, punch hole formation, folding, sorting or inserting, on one or more sheets on which an image is formed by the image forming apparatus such as an MFP.
The post-processing apparatus includes plural motors, plural solenoids and the like as plural driving devices. The power source unit of the MFP outputs power necessary for its own operation, and also outputs power necessary for the operation of the post-processing apparatus.
When the respective driving devices of the post-processing apparatus operate, current flows from the power source unit to the respective driving devices. The current increase at the time of start of the driving device, decreases after the start and is stabilized.
Thus, when the plural driving devices simultaneously start, the output current of the power source unit significantly increases. When the power source unit can not deal with the significant increase of the output current, the respective driving devices can not be started.
The cost of the power source unit having large power capacity for preventing such disadvantage is high.